In the Dagor Bragollach in F.A.455, both Galdor's father, Hador, and his younger brother, Gundor, died in the rearguard of the Elf-lord Fingolfin. Galdor then succeeded his father as Lord of Dor-lómin. In the wake of Morgoth's triumph the wife of Barahir, Emeldir, gathered the women and children of Dorthonion and led them westward; some found refuge in Galdor's domain.

The sons of Galdor, Húrin and Huor, had been taken after the Dagor Bragollach into the hidden city of Gondolin by the eagles of Thorondor. When they departed from the city (again carried by eagles) they returned to Dor-lómin where they would not reveal where they had been, even to their father.

Seven years after the Dagor Bragollach, Morgoth sent a great force against Hithlum, attacking the passes of the Ered Wethrin. Galdor defended the Eithel Sirion and was slain by an arrow.[2]

Galdor was noted for his exceptional height, even among the Edain, and was also called Galdor the Tall.[2] He led the People of Hador when they were at the peak of their power, before the Nirnaeth Arnoediad ("Battle of Unnumbered Tears").